Electrical precipitation apparatus



Jan. 9,'1934. G. GRAVE ELECTRICAL PRECIPITATION APPARATUS 2 Sheets-Sheetl Filed NOV 23 1931 f/g. e

INVENTOR.'

W ATTORNE Jan.. 9, 1934. G. GRAVE 1,943,070

ELECTRICAL FRECIPITATI/ON APPARATUS File Nov. 25,/ 1931 SheetS-She'ret 2INI/ENTQR:

Patented Jan. 9, 1934 1,943,070 ELECTRICAL PRECIPITATION APPARATUS GeorgGrave, Frankort-on-the-Main, Germany, assigner to InternationalPrecipitation Company, Los Angeles, Calif., a corporation of CaliforniaApplication November 4 Claims.

This invention relates to apparatus for electrical precipitation ofsuspended particles from gases, and particularly to an-,improvement inelectrical precipitators employing collecting electrodes pro- 5 videdwith pockets or internal spaces for the collection of the precipitatedmaterial.

The principal object of the invention is to provide automaticmaintenance of an auxiliary electric eld within said pockets or spaces,by maintaining those parts which cooperate with the collecting electrodeto form said pockets or spaces Y at a denite electric potentialintermediate the potential of the discharge and collecting electrodes,and to accomplish this without requiring the use of an auxiliaryelectric supply circuit.

According to this invention, the above result is eiected by interposingsemi-conducting material between the collecting electrode, which ispreferably grounded and is connected to one terminal of a high voltageelectric supply circuit, and the parts which cooperate with saidcollecting electrode to form the material receiving'pockets or spaces.The discharge electrode means, which are spaced in the ordinary mannerfrom the collecting electrode means and the pocket defining means, areconnected to the other terminal of' said electric supply circuit. Itwill be understood that the parts which cooperate with the collectingelectrode todene the material receiving pockets or spaces are ordinarilydisposed between the discharge electrode means and the collectingelectrode. A main precipitating electric field is thus maintainedbetween the discharge electrode means and the collecting electrodeconsidered as a whole, such main electric eld, however, terminating atthe low tension side principally at the surfaces of those parts whichare disposed somewhat outwardly from the collecting electrode proper andwhich cooperate therewith to denne the material receiving pockets orspaces. Due to the intervening layers of semi-conducting materialbetween such parts and the collecting electrode proper, however, anauxiliary electric field is also automatically established across said 5pockets or spaces, Without requiring connection of said parts to aseparate source of electric power, and this auxiliary eld tends toprevent deposition of precipitated' material on said pocket definingparts and insures that the electrically charged particles precipitatedby the main electric field are caused to pass on into the receivingpockets or spaces and upon or into close proximity to the collectingelectrode proper, where they are protected against dislodgment by thegas stream.

The potential of the auxiliary electric field and in Germany December23,

(Cl. 18S-J7) 23, 1931, Serial N0.

thus established depends upon the nature and dimensions of thesemi-conducting material interposed in the above-mentioned position. Thegreater the resistance ofthis semi-conducting material, the higher willbe the potential difference between the collecting electrode proper andthe pocket defining means, for a given total potential between thedischarge and collecting electrodes.

A further advantage of this interposed semiconducting material'is thatit prevents or damps out disruptive discharges or arcs which may tend toform between the discharge electrodes and the surfaces of the pocketdening means, by interposing sufficient resistance to-prevent anycontinued maintenance of such disruptive discharging or arcs.

The accompanying drawings illustrate embodiments of this invention, andreferring thereto:

Fig. 1 is a horizontal section of one form of discharge and collectingelectrode means according to said invention, with the electric powersupply circuit "shown diagrammatically.

. Fig. 2 is a vertical section transverse to the direction of gas flowon line 2-2 in Fig. 1.v

Fig. 3 is a longitudinal vertical section on line 3--3 in Fig. 1.

Fig. 4 is a horizontal" section showing a modied construction of thecollecting electrodes. v

Fig. 5 is a longitudinal section on line 5-5 in Fig. 4.

Fig. 6 Fig. 4.

In Figs. 1 tol 3 inclusive, the collecting electrodes comprisevertically disposed plates 1 and screens or grids 2 of suitable mesh,spaced somewhat from said plates and separated therefrom by strips 3 ofsuitable semi-conducting material such as, for example, cement or amixture of cement and asbestos. The semi-conducting 95 strips 3 may besupported upon the plates 1, for example in the manner indicated at 4,and the screens or grids 2 may be supported upon said strips, forexample, by being embedded in the is a transverse section on line 6-6 insurface layers of said strips or being secured f thereto in any suitablemanner. derstood that, when both sides of a collecting electrode are tobe utilized for precipitation, the screens or'grids above mentioned,together'with the intervening strips of semi-conducting material areprovided at both sides of the electrode plate l, as in the case of thecentral collecting electrode shown at A in Figs. 1 and 2, while whenonly one side of the collecting electrode is to be utilized forprecipitation, s'aid screen and semi- 110 It will be unwires or rods 5disposed in planes parallel to andintermediate each pair of adjacentcollecting electrodes, said discharge electrode members being spacedsomewhat from the lfurthest projecting portions of the collectingelectrodes, that is, from the screens or grids 2.

Any suitable electric supply means may be used to maintain the desiredpotential between the discharge and collecting electrodes, but I haveshown an electric circuit comprising transformer 6 and mechanicalrectifier 7, one of the output terminals of said rectier being connectedby conductor 8 to the collecting electrode plates 1 and being preferablygrounded as indicated at 9 and the other of said output terminals beingconnected by conductor 11 to the discharge electrode means 5, forexample through the frame means 12 on which the discharge electrodes aremounted.

It will be understood that the discharge and collecting electrode meansabove described may be mounted within a suitable housing or chamberprovided with inlet and outlet means for passage of gas therethroughVlongitudinally of the collecting electrodes.L The direction of gas ow is'preferably horizontal as indicated by the arrow at G in Fig. 1,although it will be understood that the gas may, if desired, be causedto pass vertically. It will also be understood that the dischargeelectrode means 5 and the frame means 12 therefor are insulated from thecollecting electrodes and from ground in any suitable manner.

It will be seen that the screens or grids 2 cooperate with the plates 1to define pockets or spaces therebetween, as indicated at 15, forreceiving precipitated material, the material so received beingprotected against dislodgment by the gas stream passing in the ducts orpassages 16 between said screens or grids and the discharge `electrodemembers 5.

In the operation of the above described apparatus, a suitable electricpotential' is maintained between the discharge and collectingelectrodes, for example, by operation of the above-described electricsupply means. The electric discharge from members 5 serves to chargesuspended particles contained in the gas passed through ducts Y orpassages 16 and the particles so charged are driven by the electricfield toward and through the screens or grids 2 and into the pockets orspaces 15. The auxiliary field maintained as above described, from thescreens or grids 2 to the respective plates 1, serves to drive suchparticles inwardly toward said plates and to hold such particles withinthe pockets or spaces 15 so that substantially all material onceprecipitated by the electric field through the pocket deflning screens 2is prevented from being subsequently picked up and carried away by thepassing gas stream. It will be observed that when the gas flow ishorizontaland the semi-conducting strips 3 are disposed vertically asshown, said strips also act as bailles so as to substantially prevent orminimize longitudinal gas flow behind the screens 2 and maintain aquiescent condition within the pockets or spaces 15.

` While I have shown particularly the provision of electric power supplymeans adapted to maintain a unidirectional electric field between theelectrodes, and while it is believed that the best results are generallyto be obtained by use of the invention in this manner, it will beunderstood that the invention is also applicable to electrical gascleaning installations in which an alternating electric field is used.

The form of construction shown in Figs. 4 to 6 inclusive, differs fromthat above described principally in 4that the pocket defining meansconstitute metal strips or bales 2 which are bent or offset in adirection transverse to the thickness thereof, so as to provide portions2a which lie relatively close to the collecting electrode plates 1 andportions 2b which are relatively remote from said plates. The portions2a are secured in any suitable manner to strips 3 of suitablesemiconducting material such as above-mentioned, which are in turnmounted upon plates 1', said semi-conducting material being disposed atall points between the strips 2 and plates 1'. The portions 2b of saidstrips are thus disposed opposite the portions of the collectingelectrode plates 1v between adjacent strips 3 and serve to definematerial receiving pockets or spaces 15' between said strip portions 2band saidportions of the plates. y

The construction may be otherwise substantially the same as abovedescribed and the operation is also substantially vthe same. Thedischarge electrodes, indicated at 5', and the collecting electrodeplates 1 are connected as before to a suitable electric supply means,and the suspended particles are precipitated by the main electric fieldinto the spaces 15' or upon the outer surfaces of the strips 2. Materialprecipitated upon said strips is carried along by the gas stream andinto the next succeeding pocket 15. The semi-conducting material 3serves to maintain said strips at a certain potential intermediate thatof the discharge and collecting electrodes, respectively, thus creatingan auxiliary electric field across the pockets 15' which acts as beforeto hold the precipitated material within said pockets. In this form ofapparatus the strips 2' preferably extend substantially vertically, and

the direction of gas flow is preferably substan.

tially horizontal, as indicated by the arrow at G.

I claim:

1. An electrical precipitation apparatus comprising a dischargeelectrode, a collecting electrode, and means disposed between saidelectrodes and electrically connected with said collecting electrode bymeans-of semi-conducting material and cooperating with said collectingelectrode to define collecting spaces for precipitated material. t

2. An apparatus for electrical precipitation comprising a dischargeelectrode, a collecting electrode spaced from said discharge electrodeand provided with. means disposed between 4said discharge and collectingelectrodes so disposed as to dene a collecting space for precipitatedmaterial adjacent said collecting electrode, said means providingopenings for passage of material into said space, semi-conductingmaterial connecting said collecting electrode and said collect-I ingspace defining means, and a source of electrical energy connected tosaid discharge and collecting electrode to maintain an electricpotential therebetween.

3. In an electrical precipitator, a collecting electrode structurecomprising an electrode member having an extended surface,semi-conducting members connected to said electrode l member anddisposed at one side thereof, and means connected to saidsemi-conducting members and electrically connected thereby with said '3electrode member at oney side thereof and cooperating therewithto dennecollecting spaces lfor precipitated material, and semi-conductingmembers electrically and mechanically connecting said means to saidelectrode member.

GEORG GRAVE.

